Apparatus for loading and unloading a supply of plates in an automated plate handler

ABSTRACT

An apparatus is provided for positioning a plurality of cassettes within an automated printing plate handler. In a plate handler, a plurality of cassettes each contain a supply of printing plates for delivery to an automatic plate-recording device. The apparatus includes a separate support table for supporting each of the plurality of cassettes within the plate handler and an elevator device for moving each of the support tables along a vertical axis of the automated plate handler. The automated plate handler is configured to automatically position a selected cassette in a first position to facilitate removal of the cassette from the handler. The plate handler further includes a platform, which substantially forms an extension of the support table supporting the selected cassette in the first position. The platform provides a second position, at which the selected cassette is to be one of, loaded or unloaded. The selected cassette may be filled with a new supply of plates on the platform or the selected cassette may be removed from the platform and replaced by a another cassette.

BACKGROUND OF THE INVENTION

[0001] Printing processes utilize a vast array of different technologiesto transfer written content to various distribution media. Organizationsusing varying printing processes include modest-volume quick printers,book and financial publishers, newspaper companies, forms companies, allsizes of commercial printers (for advertising etc.), and, Publicationprinters (for magazines and periodicals). These types of organizationshave a common process whereby information is transferred from someoriginal layout form to an intermediate aluminum or polyester platematerial which is then hung on a standard printing press to enablemultiple identical replication of that information on paper or somesimilar print media.

[0002] This process has typically been performed by optically creating apolyester film which contains the information, optically transferringthe information from the film to a plate material by use of a lighttransfer or contact to a light-sensitive chemical emulsion which isbonded to the plate, and then hanging the developed plate on a press inalignment (one for each color separation desired). The plates rotatealong with the press cylinder and alternately come in contact with inkrollers and then an intermediate transfer blanket. The ink which isaccepted by the transfer blanket then transfers the information to thepaper during rotational contact.

[0003] Recently the development of computer-to-plate, hereinafter C2P,systems and processes have provided alternative printing options. TheC2P process eliminates the film as an intermediate transfer mechanismand allow the optical exposure of the plate directly. This reduces thenumber of steps required in the printing process of the information andpotentially reduces the cost related to the generation of theintermediate film and its handling. C2P systems more readily allow aprocess which creates plates for shorter-run printing (below around50,000 impressions).

[0004] In basic terms, a C2P system accepts primarily Postscript inputjobs/pages. These jobs are controlled through execution by priority andscheduling workflow software. Jobs are then sent through a raster imageprocessor to a platemaker for exposure. The data is being transformedthroughout this process. The platemaker engine takes this data andprints it on a metal sheet of aluminum which is later notched, bent,hung on the press, inked and made ready to image paper. An imagingengine and process for imaging a plate is described in commonly ownedU.S. Pat. No. 5,345,870, hereby incorporated by reference into thepresent application.

[0005] The inclusion of a C2P system into a printing operation suggestsa greater extent of automation which can be achieved. A full C2P processcan automate, through the use of computers and special equipment, thetransfer of information from the original layout to the press plate. Assuch, C2P is not only an improvement in the specialized equipment butalso in the process which utilizes that (equipment. Viewing C2P as aprocess includes a high level of workflow management to replace manualeffort with computer-driven effort with a goal to increase productivityand efficiency. Workflow encompasses such concepts as queue management,color calibration, revision control, press consumables control,inventory tracking, job and cost tracking, etc.

[0006] Also included in the automation of a C2P system is the mediahandling. It is necessary to supply plates individually from a platesupply area to the platemaker engine and it is desirable to reduce theamount of operator handling involved. Unexposed plates are normallysupplied in packages of 25 to 100 with interleaf sheets between theplates for protecting the sensitive emulsion side of the plates, whichis extremely sensitive to scratches. The stack of plates needs to beloaded into a supply area of a platemaker in a manner to keep the stackof plates aligned with automation mechanisms for removing a plate fromthe stack, and for discarding the interleaf sheet from the stack. Thesefunctions are optimally performed within a covered light-tightenvironment to prevent unintentional exposure of the light sensitiveplate surface. The platemaker engine requires plates of varying sizesand formats on demand. It is beneficial to present a variety of platesizes and formats to an automated mechanism for selecting the plateneeded by the platemaker engine. It is important to be able to reloadthe plate supply area without interrupting the operation of theplatemaker engine. These functions generally will maximize the output ofthe platemaker engine, by eliminating time which an operator wouldmanually handle the plates and during which the platemaker engine mightbe interrupted.

[0007] Accordingly it is an object of the present invention to providean automated C2P system having a workflow software capable ofcontrolling and sequencing the tasks performed by the C2P system fromaccepting a job input to the system as Postscript and output the jobfrom the system as exposed images on printing plates.

[0008] It is a further object of the invention to increase productivityand efficiency in a C2P system by providing automated queue management.

[0009] It is a specific object of the invention to automate theoperation of supplying plates on demand from a plate storage area withina C2P system to the platemaker engine.

[0010] It is a further object of the invention to provide a platehandling mechanism to position a plurality of plate cassettes containingvarying plate sizes within the plate storage area, making a desiredplate cassette accessible to a plate picking mechanism.

[0011] It is another object of the present invention to automaticallyremove and discard the interleaf sheets from between plates after aplate is individually removed from the stack of plates.

[0012] It is another object of the invention to automatically pick aplate from the top of a stack of plates and deliver the plate to theplatemaker engine in a manner which accommodates a variety of platesizes and formats.

SUMMARY OF THE INVENTION

[0013] A method for handling, loading and unloading a plurality ofcassettes containing a supply of plates in an automated plate handlerincludes supporting each cassette on a support table within the platehandler. The support tables and the cassettes of plates supported on thetables are automatically positioned in order to place a cassette to beremoved from the plate handler in a cassette loading position. Thecassette to be removed is moved horizontally along the table onto aloading platform adjacent to the cassette loading position guiding thecassette to be removed off of the support table and onto the loadingplatform while removing the cassette from the plate handler.

[0014] An apparatus for handling, loading and unloading a plurality ofcassettes containing a supply of plates in an automated plate handlerincludes support tables supporting each of the cassettes within theplate handler. The support tables and the cassettes of plates on thesupport tables are automatically positioned in order to place a cassetteto be removed from the plate handler in a cassette loading position. Thecassette to be removed is moved horizontally by a first mechanism alongthe table and onto a loading platform adjacent to the cassette loadingposition. A guide member guides the cassette to be removed off of thesupport table and onto the loading platform while the cassette isremoved from the plate handler.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The objects and features of the invention will be betterunderstood and further objects and advantageous of the invention willbecome apparent in the following detailed description of the invention,when taken with the accompanying drawing(s), in which:

[0016]FIG. 1 is a schematic illustration of an electronic prepresssystem employing a platesetter shown from a side view with a platehandler and plate picker mechanism according to the present invention;

[0017]FIG. 2 is a partial sectional front view of the plate handlerviewed in FIG. 1;

[0018]FIG. 3 is an isometric view of an assembly portion of the platehandler shown in FIG. 2, particularly featuring an elevator mechanismand a table supporting mechanism according to the present invention;

[0019]FIG. 4 is a detailed isometric view of the plate picker mechanismshown in FIG. 1;

[0020]FIG. 5 is a simplified top view of the picker mechanism of FIG. 4positioned over a handler cassette within the plate handler according tothe present invention;

[0021]FIG. 6 is a side view of a portion of the plate handler showingthe plate picker in the process of picking a plate from a cassette, andalso featuring a slip sheet removal mechanism according to the presentinvention;

[0022]FIG. 7 is an isometric view of a plate cassette used in the platehandler according to the present invention; and

[0023]FIG. 8 is a detailed side sectional view of a portion of a platecassette as shown in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The computer to plate imaging system shown in FIG. 1 andgenerally referred to as reference number 10, is a complete system forplate production, where digital data files representing a publication(or printed image) are input to the system 10, and plates ready to go ona printing press are output from the system 10. Most of the operation ofthe system is automated, requiring a minimum of operator intervention.The system is comprised of a front-end server 12, a raster imageprocessor (RIP) 14 and a platemaker or platesetter 16. The front-end 12sends jobs to the platesetter 16. The platesetter 16 has three majorcomponents. An optional on-line plate handler 18, the imaging engine 20and an optional on-line plate processor/plate stacker 22. The platehandler 18, hereinafter handler, contains a supply of plate containersor cassettes 24. The handler can hold as little as two cassettes or asmany as three, four, or five depending on user requirements. Eachcassette is a light tight container that houses a stack of plates 26.The cassettes 24 can be vertically adjusted by the handler 18 to makeplates 26 stored within a particular cassette available to a plateshuttle mechanism 28, hereinafter referred to as the picker 28. Thepicker 28 removes a single plate from the selected cassette andtransports the plate between the handler 18 and the engine 20, whichwill be described in detail hereinafter.

[0025] The primary function of the handler 18 is to make plates 26available on demand to the imaging engine 20. A multitude of plates 26are stacked in each cassette 24 and the cassettes 24 are side-loadedinto the handler 18 by an operator. Between each plate in a stack theremay be a protective interleaf sheet or slip sheet which is removed bythe handler 18 and discarded by a slip sheet removal mechanism 25. Thehandler 18 receives commands from the engine 20 by workflow software,which provides instructions to the handler 18 about what cassette 26needs to be accessed to make a plate available to the picker 28 so theplate may be conveyed to the imaging engine 20. The handler 18 in turnprovides status information to the engine 20 through the workflowsoftware to make full interaction with the system 10 possible.

[0026] The front-end 12 sends data to the engine 20 through an interfaceconnection. Typically this data represents a “job” which requires theimaging of plates. This data contains information about the job'srequirements, such as the type of plate, its size and plate thickness,the number of plates that are part of the same job, etc. The engine 20interfaces electrically with the handler 18 to exchange machinefunctional and operation data which is input into the workflow software.The handler 18, through the engine 20, sends data to the workflowsoftware from data stored in each loaded cassette 26 representing platesize and quantities available in the cassettes 26. The handler 18 hasthe capability of reading an ID tag on each cassette which has adescription of the plate type inside. This ID tag is in the form of abar-code or other means. If a required plate size is unavailable, theengine 20 notifies an operator through a platemaker control terminal 30,so the operator can load the needed cassette into the handler 18. Theengine 20 passes information to the handler 18 defining the next platesize or thickness required for imaging and which cassette 26 is to beplaced in the queue, or in the correct position for access by the picker28. The cassettes 26 store different sizes and/or thicknesses of plates26 so the handler 18 positions a specific cassette 24 so that the picker28 can access the required plate inside the specific cassette. Thehandler 18 insures the slip sheet, if present, has been removed from thesurface of the top plate with the slip sheet removal mechanism 25. Thepicker 28 then moves over the positioned cassette, the plate is“picked,” and the picker 28 returns to the imaging engine (home)position to deliver the plate. The imaging engine 20 accepts the plateand while the picker is in the engine 20 in the home position, thehandler 18 is free to position the cassettes 24 in preparation for thenext plate to be imaged.

[0027] Referring to FIG. 2, some basic elements of the handler 18 areshown. The handler 18 has a support frame 32 which surrounds severaltables 34, 36. The lowermost table 36 is attached to and supported by abrace 38 on the underside of the lowermost table 36. The brace 38 isattached to an elevator mechanism, referred to generally as 40 and to bedescribed hereinafter, which raises and lowers the brace 38 and thelowermost table 36 supported by the brace 38. The upper three tables 34positioned above the lowermost table 36 rest upon the lower table 36 ontable spacers 42 which are secured to the outer ends of the undersidesof the upper three tables 34. In FIG. 2, the upper three tables 34 areshown being supported by a table support mechanism, referred togenerally as 44 and to be described hereinafter, which separates thetables to allow clearance space for the picker to enter into above thecassette from which a plate is going to be picked. When the tablesupport mechanism 44 is inactive, the table spacers 42 contact the tableimmediately below the table which the spacers are attached to, in amanner so as to support that table. The tables 34, 36 can be positionedby the elevator mechanism 40 as a group, with the three upper tables 34resting on the lowermost table 36 on the brace 38 of the elevatormechanism 40.

[0028] Referring additionally to FIG. 3, the support frame 32 has fourvertical support beams 46 provided with guide tracks 48 for guiding thetables while being raised or lowered. Each table has four rotatableguide wheels 50 (only two shown as viewed in FIG. 2) which ride in theguide tracks 48 at the corners of each table. The table supportmechanism 44 comprises four vertical shafts 52 with bearing mounts 54 atthe upper ends of each shaft 52. The shafts 52 are rotatable relative tothe bearing mounts 54 which are attached to the topside of the supportframe 32. The support frame 32 has bores (not shown) which the shaftspass through to extend downward to the tables 34, 36. At the lower endsof the shafts 52 are support bars 56 which protrude horizontally outwardfrom the shaft 52 at a right angle therefrom, and lower bearing mounts58 attached to the four vertical support beams 46. In an inactiveposition, the support bars 56 face outward and away from the tables, asshown in FIG. 3. A linkage 60 connecting the shafts 52 transmits rotarymotion from a drive motor 62 to rotary plates 64 fixed to the tops ofeach shaft 52 and to the shaft of the drive motor 62. Upon apredetermined rotation by the drive motor 62, the linkage 60 connectingthe rotary plates causes the four shafts 52 to rotate 90 degrees,positioning the horizontal support bars 56 facing inward toward thetables, in the active position as in FIG. 2. The support bars 56 are inposition to support the tables 34 above the cassette 24 to be accessedby the picker 28.

[0029] The elevator mechanism 40 comprises a chain drive system havingfour chain drives 66, one mounted on each support beam 46. Two rotatablesprockets 68, 70 are mounted on each support beam 46 in an upper andlower position to cooperate with the chains 66 and transmit rotarymotion of the sprockets 68, 70 into linear motion of the chains 66. Thelower sprockets 70 are attached to two horizontal shafts 72 whichtransmit rotary motion from a main drive shaft 74 through several gearboxes 76 and couplings 78. The main drive shaft 74 is powered by a drivemotor 80 through a belt 82 and pulley 84 connection.

[0030] The brace 38 is connected to the chains 66 on the inner sides ofthe support beams 46 so that upon rotation of the drive motor 80, thechain drive system raises or lowers the brace 38, the lowermost table36, and any upper tables 34 resting thereon which are not supported bythe table support mechanism 44 at the time.

[0031] Referring now to FIG. 4, the picker 28 is shown supported onparallel rails 90 which are fixed to the interior of the enginecompartment 20 (FIG. 1). Complementary rails 92 are mounted inside ofthe handler 18 as shown cross section in FIG. 2 and isometrically inFIG. 3, allowing the picker to move smoothly between the engine 20 andhandler 18. The rails 92 inside the handler are secured to the supportbeams 46 of the handler frame 32. The picker 28 has a carriage 94 whichis supported on the rails (90 or 92 depending on whether the handler isin the engine or the handler respectively) by three guide wheels 96which engage the rails 90 (or 92) on each side of the carriage 94. Alsotwo friction wheels 98 engage the rails 90 (or 92). The friction wheels98 are driven by a motor 100 mounted on the carriage 94 through aconnection to a drive shaft 102 and a belt and pulley mechanism 104 oneach side of the carriage 94. The motor 100 operates in two directionsto effectively propel the picker carriage 94 in forward and reverse fromthe engine compartment 20 to the handler 18. The carriage 94 supportsthree rows 106, 108, 110 of suction cups and an associated vacuummanifold 112 and vacuum tubing (not shown) between the manifold 112 andthe three rows 106, 108, 100 of suction cups. The suction cups 114 aremounted on spring loaded fittings 116 to allow compression of thesuction cups 114 against a plate during picking to ensure attachment ofthe plate to the picker 28. The first row 106 of suctions cups thatextends the furthest into the handler 18 is pivotable with respect tothe carriage 94. An eccentric drive 118 and linkage 120 pivots the firstrow 106 of suction cups in a “peeling” motion. The eccentric 118 isdriven by a motor 122 mounted on the carriage 94 to break or peel theedge of the plate being picked away from the stack. The middle row 108of suction cups remains fixed with respect to the picker carriage 94.The third row 110 of suction cups slides out from the middle row 108 ofsuction cups. Two circular rails 124, 126 are mounted for slidingthrough complementary bearings (not shown) in the carriage body 94 onthe both sides of the picker 28. On the right side of the picker viewedin FIG. 4, the circular rail 126 has a friction drive wheel (not shown)is in driving contact with the circular rail 126. The drive wheel isdriven by a drive motor 128 through a belt and pulley mechanism (notshown), all of which are mounted to the carriage body 94 so as totransmit rotary motion of the drive wheel into linear motion of therails 126, 124 relative to the carriage body 94. The third row 110 ofsuction cups being movable relative to the other rows 106, 108 ofsuction cups expands the overall size of the picker 28 and the coveragearea of the suction cups 114 to accommodate for various sized plates.

[0032]FIG. 5 illustrates a simplified top view of the picker 28positioned over a cassette 24 in the handler. The first row 106 ofsuction cups 114 is positioned near an inner edge 130 of the cassette 24against which the plates are referenced regardless of the plate size.Four different plates having different sizes are depicted by dashedlines and are indicated as plates A, B, C, and D. Plate A is thesmallest plate and the middle row 108 of suction cups of the picker 28is positioned near the opposite edge 132 of plate A from the referenceedge 130. The middle row 108 has a fixed position relative to the firstrow 106 (excepting that the first row is pivotable) to pick up plate Awithout the use of the third row 110 of suction cups. The third row 110is shown in an extended position by solid lines, at the far edge 134 ofthe largest plate D opposite from the reference edge 130. The third row110 of suction cups is also shown by dashed lines in a non-extendedposition. The third row 110 of suction cups is used to expand the sizeof the picker 28 to cover the areas for various size plates, such as B,C, and D, larger than the smallest plate A and smaller than or equal tothe largest plate D, as indicated by arrow 136. Arrow 138 shows therelative movement of the picker 28 including all three rows 106, 108,110 of suction cups 114 with respect to the handler cassette 24 and theengine.

[0033] Referring now to FIG. 6, the slip sheet removal mechanism isgenerally indicated as 25. The mechanism 25 is for the purpose ofpreventing a slip sheet 140 from sticking to the bottom of a plate 142which is attached to the picker 28, securing the slip sheet 140 on thetop of the stack of plates in a cassette 24 to the slip sheet removalmechanism 25, and subsequently completely removing the slip sheet 140from the stack of plates in the cassette 24. The mechanism 25 comprisesa plurality of suction tubes 144 mounted on a first pivotable shaft 146,an optional peeler air blast 148, a plurality of fingers 150 mounted ona second pivoting shaft 152, a plurality of nip wheels 154 mounted on athird pivoting shaft 156 (only one of each seen in drawing due to sideview), and a rotatably driven roller 158 positioned below the nip wheels154 which are in rolling contact during part of the slip sheet removalprocess, to be described hereinafter. The suction tubes 144 are fixed tothe pivoting shaft 146 to pivot upon being driven by motor 160 through adrive belt and pulley connection 162. The fingers 150 are fixed topivoting shaft 152 which is driven by a similar drive connection to amotor (not shown). The nip wheels 154 are each mounted to an extensionarm 164 which is attached to a bracket 166 mounted on the pivoting shaft156. The extension arm 164 is spring loaded at the connection to thebracket to allow for the extension arm 164 to pivot or give slightlywhile pressure is applied between the nip wheel 154 and the roller 158.The shaft 156 is rotated in forward and reverse by the drive motor 168through a drive belt and pulley connection 170. The roller 158 is drivenby a motor 172 also through a belt and pulley connection 174. It will beunderstood by those skilled in the art that equivalent means forrotating the pivoting shafts 146, 152, 154, and rotating roller 158, maybe substituted therefor without departing from the spirit of theinvention. The driven shafts and motors for driving the shafts are allmounted to a mounting bracket 176 which is connected to the supportbeams 46 of the handler 18. Operation of the slip sheet removalmechanism 25 will be described hereinafter.

[0034] Referring now to FIG. 7 and FIG. 8, a cassette 24 for loadinginto the plate handler is shown. The cassette has a removable cover 180,which is removed and replaced in a vertical direction relative to arectangular bottom container 182 as indicated by arrows. The bottomcontainer 182 comprises a base plate 184 surrounded by four aluminumside extrusions 186. The extrusions 186 are attached at the four 90degree corners by spring clips and adhesive (not shown). The base plate184 is contained within a slot 188 in the edge of each extrusion 186 andis held in place with an adhesive on the top side 190 of the base plate184 and a piece of continuous round flexible urethane belting 192 on thebottom side of the base plate 184. The round belting 192 is retained ina thin groove 194 provided in the extrusion 186.

[0035] Three channels 196 (one shown) are fastened to the bottom side ofthe base plate 184. The channels 196 act as reinforcing stiffeners forthe bottom container 182, and also are housings for three locator bars198. Each locator bar 198 is attached within a channel 196 by anadhesive. An adjustable stop 200 is provided on each locator bar 198 toslide along the locator bar and be fastened to a set position by a lockscrew 202 which screws into holes 204 drilled into the locator bars 198.The three adjustable stops 200 locate and secure a stack of plates 26against several reference blocks 206 fastened to the side extrusions186. The adjustable stops 200 allow multiple sizes of plates 26 to beheld against the reference blocks 206 within a single bottom container182. The base plate 184 is provided with embossed areas 208 for thereference blocks 206 to be set within, which prevents the platesreferenced against the reference blocks 206 from sliding between thereference block 206 and the base plate 184 and maintaining alignment ofthe plates with respect to the reference block 206.

[0036] The cover 180 comprises a top plate 210 and four side extrusions212 surrounding the top plate 210. The extrusions 212 are fastenedtogether at the four corners of the top plate 210 by spring clips andadhesive (not shown). The top plate is secured to a ledge portion 214 ofthe extrusions 212 by an adhesive. Two of the four side extrusions havea handle portion 216 formed in the extrusion 212 which cooperate withhooks on the undersides of the cassette tables in the handler to removeand replace the cassette cover (to be described hereinafter). The insideof the top plate 210 has a layer of foam 218 attached, to ensure thatthe plates on the top of a full stack of plates 26 do not slide over thetops of the reference blocks 206 during loading of a cassette 24 intothe handler 18. The cover 180 and the bottom container 182 areconstructed from light proof materials, so that when the plates areenclosed within a covered cassette, there is no exposure of the lightsensitive plate contained within the cassette. The attachment areabetween the bottom extrusions 186 and the cover extrusions 212 hasmagnetic strips 220 which ensure the cover 180 is attached securely tothe bottom container 182 and that no light will enter the cassette 24during handling.

[0037] The side extrusions 186 are provided with a beveled portion 230which aid in the loading of the cassette 24 into the plate handler 18.The handler 18 has a loading platform 232 shown in FIG. 2, extendinghorizontally from the vertical beams 46 of the handler. The loadingplatform 232 has rows of grooved wheels 234 mounted for rotation withinthe loading platform 232. The grooved wheels 234 cooperate with thebeveled portion 230 of the side extrusions 186 of the cassette 24 duringloading and serve to register the cassettes in a reference positionwithin the handler. All tables 34 and 36 within the handler are alsoprovided with the rows of grooved wheels to facilitate smooth and easyloading of the cassette from the loading platform onto the supporttables in the handler, while maintaining the cassette in register. Thebeveled portions 230 cooperated with the V-grooved surface 236 of thegrooved wheels 234 on opposite outer sides of the cassette 24 for properalignment. The cassette is designed to align the plates inside thecassette against the reference blocks provided on the interior of thecassette, and also register the cassette into a reference positionwithin the handler, as shown in FIG. 5, regardless of the plate sizecontained in the cassette. The parallel rails 92 in the handler arefixed relative to the wheels of the selected table in the accessposition. This ensures the registration of the plates within thecassette relative to the rails 92, and the registration is transferredto the complementary rails 90 in the engine compartment, and thereby theplate is delivered in register into the engine from the handler.

[0038] Additional locator stops 238 are provided on each table to assistin registering the cassette 24 in the loading direction so that thecassette 24 is pushed into the handler 18 along the grooved wheels 234of the table 36, but only to a predetermined location so that thecassette 24 is registered with respect to two dimensions and to thepicker rails 92. These additional locator stops 238 are spring loadedand are located between the grooved wheels 234 within each row ofgrooved wheels on a table 36. The stops 238 contact an underside 240 ofthe side extrusions 186 while the cassette 24 is being loaded, and whenthe stop 238 comes into contact with a recess (not shown) formed in theunderside of the extrusion, the spring force behind the stop 238 forcesthe stop into the recess and locks the cassette 24 into a predeterminedposition on the table. The wheels 234 register the cassette with respectto the two reference blocks 206 on one side of the cassette, while thelocator stops 238 within the rows of the wheels 234 register thecassette 24 with respect the third, alone reference block 206 on theneighboring side of the cassette. Then the plates are registered in aknown location relative to the picker, as depicted in FIG. 5.

[0039] The loading platform 232 can be incorporated into the design ofthe doors and covers for enclosing the handler in a light tightenvironment. The loading platform can function both as a door into thecassette loading area, and as the loading platform. This is accomplishedby providing an attachment hinge on the handler frame for the loadingplatform 232 to pivot between the two functional positions. The loadingplatform 232 is pivoted up for a closed door position, and down andhorizontally as shown in FIG. 2 for an open, cassette loading position.

[0040] Cassettes loaded into the handler house the plates. At any onetime, a cassette holds only like plates (same type, gauge, size, etc.).Typically, there is a maximum of 50 plates of 0.012″ gauge, 75 plates of0.008″ gauge, or 100 plates of 0.006″ gauge, in a single cassette. Thereare several distinct cassette sizes. A cassette of a specific size holdsa range of plate sizes inside, however only one size plate is loadedinto a cassette at any one time. Fillers or guides are used to take-upthe space between plate and cassette boundaries. The reference positionof the plates within the cassette is described above with reference toFIG. 5. Packaging of plates within a cassette is related to both handleroperation and cassette transportability. There may be a mix of cassettesin the handler (two, three or four cassettes). All cassettes can bedifferent from each other, in that each houses a distinct set of platecharacteristics (type, size, gauge, etc.) There may be instances wheresome or all cassettes inside the handler have the same platecharacteristics.

[0041] Now, with reference to all the Figures, the method for using theplate handler 18 and picker 28 will be described. The primary functionof the handler 18 is to position a required plate on demand in an accessposition for the picker 28, which picks and delivers the required plateto the engine 20. Once the handler 18 receives a request from the engine20 for a specific plate, the following actions take place in thehandler, in cooperation with the engine 20. The picker 28 begins in thehome position within the engine 20. The slip sheet removal mechanism 25is positioned with the suction tubes 144, fingers 150, and nip wheels154 retracted (as shown in dotted lines for the suction tubes and nipwheels in FIG. 6) to clear the path of the tables 34, 36 forrepositioning by the elevator mechanism 40. The elevator mechanism 40moves the brace 38, lower table 36, and upper tables 34 supportedthereon, if any, to a cover removal/replacement position. In the coverremoval/replacement position, the selected table 36 is located directlybelow the table 34 supported by the support bars 56 of the table supportmechanism 44. Hooks on the bottom of the supported table 34 engage thecover 180 of the selected cassette 24 for either removal or replacement,so that the cover 180 is separated from or rejoined with the selectedcassette 24.

[0042] In FIG. 2, the cover removal/replacement position for the lowertable 36 is at a position where the open cassette 24 on the lower table36 contacts the cover 180 supported by the table 34 immediately abovethe lower table 36 held by the support bars 56. When the selectedcassette 36 is in the cover removal/replacement position, the uppertables 34 are all then supported by the brace 38. Then the support bars56 and shafts 52 are turned 90 degrees by means of the linkage 60 anddrive motor 64. Once the support bars 56 are retracted from the path ofmotion of the tables 34, 36, the elevator mechanism 40 moves to thecover removal/replacement position for the next selected table andcassette. The table support mechanism 44 moves the support bars 56 intothe supporting position underneath the table directly above the selectedcassette 24. The elevator mechanism 40 then moves the selected tabledown thereby separating the cover 180 of the selected cassette 24 fromthe selected cassette 24 so that the picker can access the plates 26contained within the cassette 24.

[0043] The picker 28 is then moved from the home position in the engine20 into the handler 18 along the rails 90 and 92. Depending on the sizeof the plate in the selected cassette 24 the picker 28 adjusts the thirdrow 110 of suction cups relative to the middle row 108 of suction cupsto accommodate for various plate sizes, if necessary (FIG. 5). Theelevator mechanism 40 moves the selected cassette 24 and plates thereinupward to come into contact with the suction cups 114 on the picker 28(FIGS. 4 and 6). The suction cups 114 retract into the spring loadedfittings 116 to accommodate for variations in the stack height of theplates 26 in the cassettes 24, as the elevator 40 moves the cassette 24up to the picking position which is at a set vertical height relative tothe picker rails 90 b, 92 b. Therefore for a maximum stack height of afull stack of plates, the suction cups 114 compress against the springloaded fittings 116 and retract a length into the fittings, and for adepleted stack of plates, the suction cups 114 compress against thespring loaded fittings and retract substantially the same length minusthe height of the stack depletion. The spring loaded fittings 116 alsoensure that the plate and the suction cups 114 make contact to securethe plate onto the picker 28. After the plate is attached to the picker28 by the vacuum suction, the first row 106 of suction cups on thepicker 28 is pivoted upward, peeling back the edge of the plate 142 andcreating a gap between the plate 142 and the slip sheet 140 underneath.

[0044] The slip sheet removal mechanism 25 activates the peeler air flow148, and the fingers 150 are pivoted into position to hold down the edgeof the slip sheet 140 while the elevator mechanism 40 lowers thecassette 24 to a slip sheet removal position. The peeler air blast 148remains on while the cassette 24 moves downward to separate the slipsheet 140 from the bottom of the plate 142 being picked by the picker28, which may stick to the plate due to electrostatic charge. Thefingers 150 are pivoted away from the slip sheet 140 and the suctiontubes 144 are pivoted into position above the slip sheet edge. Thesuction cups on the ends of the suction tubes are compliant and flexibleso that when the vacuum is applied and contact is made between a suctioncup and the slip sheet, the slip sheet material is drawn into thesuction cup and the separation of the slip sheet from the plate below itis initiated. The compliant suction cup deforms to break the slip sheetaway from the lower plate as typically an attractive force existsbetween the slip sheet and the plate. This is also an important step inthe process of removing the slip sheet because the slip sheet may be aporous material and the vacuum applied through the suction tubes canpass through the slip sheet material and be applied to the plate below,which is undesirable when attempting to remove the slip sheet. Theselected cassette 24 is elevated to bring the slip sheet 140 intocontact with the suction tubes 144 while the vacuum is on. The suctiontubes 144 pivot upward slightly to break the adhesion of the slip sheet140 to the plate below. The elevator 40 then moves the selected cassette24 downward from the slip sheet removal mechanism 25 and the suctiontubes 144 pivot back downward to the roller 158 with the slip sheet 140attached. The vacuum for the suction tubes 144 is turned off and theslip sheet 140 is released to the rotating roller 158 to pull the slipsheet 140 away from the stack. The nip wheels 164 pivot from theposition shown in solid lines to the position shown in dotted lines tocooperate with the roller 158 and remove the slip sheet 140. A sensor(not shown) indicates that the removal of the slip sheet 140 iscompleted and the rotating roller 158 is then halted. Meanwhile thepicker 28 lowers the first row 106 of suction cups from the peelingposition, and the picker 28 travels back into the engine 22 to the homeposition. For the next plate to be selected by the picker 28, the stepsare partially repeated if the same cassette 24 is being picked from, orthe steps are repeated from the beginning of the sequence for anothercassette.

[0045] In order to load cassettes into the handler, the following methodsteps occur in conjunction with the plate handler apparatus and theworkflow software as described previously. The handler has sensorspositioned appropriately (not shown) to monitor the level of the platescontained in each cassette. Additionally the handler has the capabilityof knowing the types of plates available so that when a plate needed bythe engine is not available, or upon a sensor detecting an emptycassette, a signal is communicated to the engine and the operator isalerted through the operator control terminal 30.

[0046] The picker 28 is returned (if not already there) to begin in thehome position within the engine 20. The slip sheet removal mechanism 25is positioned with the suction tubes 144, fingers 150, and nip wheels154 retracted (as shown in dotted lines for the suction tubes and nipwheels in FIG. 6) to clear the path of the tables 34, 36 forrepositioning by the elevator mechanism 40. The elevator mechanism 40moves the brace 38, lower table 36, and upper tables 34 supportedthereon, if any, to the cover removal/replacement position previouslydescribed. Then the support bars 56 and shafts 52 are turned 90 degreesby means of the linkage 60 and drive motor 64. Once the support bars 56are retracted from the path of motion of the tables 34, 36, the elevatormechanism 40 moves to the cassette loading position for the selectedtable and cassette needing replacement. The cassette loading position islocated where the selected table is adjacent to the loading platform 232shown in FIG. 2 extending out from the handler 18 to support thecassette 24 to slide horizontally between the selected table and theloading platform 232 during loading and unloading. Covers and doors (notshown) are provided to enclose the entire handler frame to maintain thecassette in a light tight environment. The doors are provided to accessthe interior of the handler and at this time the door locks are releasedto allow operator access. Then the empty cassette is removed by slidingthe cassette out horizontally in along the path formed by the groovedwheels in the selected table and the loading platform, and then thecassette is either reloaded or replaced with another cassette. Thecassette presence is monitored by sensors. After detecting the cassetteon the selected table, the handler waits for the doors to be closed andthen the door locks are activated. The elevator moves up to the coverremoval/replacement position for the selected cassette and normaloperation is resumed.

[0047] It will be understood that the preferred embodiment of the systemdescribed herein being a platesetter for imaging aluminum plates, can beused also with polyester plates, can be modified to perform as aproofing device rather than a platesetter, such as in commonly owned,pending U.S. application Ser. No. 08/496,714, entitled “ElectronicPrepress System With Multi-Function Thermal Imaging Apparatus,” herebyincorporated by reference. Additionally the apparatus described hereinis applicable to production of thermally recorded printing plates aswell as photosensitive lithographic printing plates recorded by lightexposure, with various modification to the system's processing andimaging components, as appreciated by those familiar with the art.

[0048] While this invention has been described in terms of variouspreferred embodiments, those skilled in the art will appreciate thatvarious modifications, substitutions, omissions and changes may be madewithout departing from the spirit thereof. Accordingly, it is intendedthat the scope of the present invention be limited solely by the scopeof the following claims, including equivalents thereof.

We claim:
 1. A method for handling, loading and unloading a plurality ofcassettes containing a supply of plates in an automated plate handler,comprising the steps of: a. supporting each cassette on a support tablewithin the plate handler; b. automatically positioning the supporttables and the cassettes of plates supported on the tables, and placinga cassette to be removed from the plate handler in a cassette loadingposition; c. moving the cassette to be removed horizontally along thetable and onto a loading platform adjacent to the cassette loadingposition; and d. guiding the cassette to be removed off of the supporttable and onto the loading platform while removing the cassette from theplate handler.
 2. The method according to claim 1, wherein the step ofautomatically positioning the support tables comprises the steps of: a.moving a table from an access position in which the cassette supportedon the table is open to allow a plate to be removed from the opencassette and a cover for the open cassette is supported by an adjacenttable, to a cover replacement position closer to the adjacent table inwhich the cover is replaced on top of the open cassette; and b.repositioning all the tables as a group and aligning the cassette to beremoved adjacent to the cassette loading position.
 3. The methodaccording to claim 2, further comprising the steps of: a. aligning acassette to be loaded into the plate handler with guides provided on theloading platform; b. guiding the cassette to be loaded from the loadingplatform onto the support table in the cassette loading position whileloading the cassette into the plate handler; and c. moving the cassettehorizontally along the loading platform and onto the table adjacent tothe cassette loading position.
 4. The method according to claim 2,further comprising: a. monitoring the support table adjacent to theloading platform for a cassette to be loaded onto the support table; b.positioning a table supporting a selected cassette at a cover removalposition; and c. separating the table supporting the selected cassettefrom an adjacent table to remove a cover from the selected cassette thatis supported by the adjacent table to open the selected cassette.
 5. Themethod according to claim 3, further comprising the step of readinginformation from an information source attached to the cassette whilemoving the cassette from the loading platform onto the table adjacent tothe cassette loading position.
 6. An apparatus for handling, loading andunloading a plurality of cassettes containing a supply of plates in anautomated plate handler, comprising: a. support tables supporting eachof the cassettes within the plate handler; b. means for automaticallypositioning the support tables and the cassettes of plates on thesupport tables, and placing a cassette to be removed from the platehandler in a cassette loading position; c. means for moving the cassetteto be removed horizontally along the table and onto a loading platformadjacent to the cassette loading position; and d. guide means forguiding the cassette to be removed off of the support table and onto theloading platform while removing the cassette from the plate handler. 7.The apparatus according to claim 6, further comprising means for readinginformation from an information source on each of the cassettes.
 8. Theapparatus according to claim 6, wherein said means for automaticallypositioning the support tables first moves a table from an accessposition in which the cassette supported on the table is open to allow aplate to be removed from the open cassette and a cover for the opencassette is supported by an adjacent table, to a cover replacementposition closer to the adjacent table in which the cover is replaced ontop of the open cassette, and then repositions all the tables as a groupand aligns the cassette to be removed adjacent to the cassette loadingposition.
 9. The apparatus according to claim 8, further comprising: a.means for guiding the cassette to be loaded onto the loading platformand from the loading platform onto the support table in the cassetteloading position while loading the cassette into the plate handler; andb. means for moving the cassette horizontally along the loading platformand onto the table adjacent to the cassette loading position.
 10. Theapparatus according to claim 8, further comprising: a. means formonitoring the support table adjacent to the loading platform for acassette to be loaded onto the support table; b. means for positioning atable supporting a selected cassette at a cover removal position; and c.means for separating the table supporting the selected cassette from anadjacent table to remove a cover from the selected cassette that issupported by the adjacent table to open the selected cassette.
 11. Theapparatus according to claim 9, further comprising means for readinginformation from an information source attached to the cassette whilemoving the cassette from the loading platform onto the particular tablein the loading position.
 12. An apparatus for handling, loading andunloading a plurality of cassettes containing a supply of plates in anautomated plate handler, comprising: a. support tables supporting eachof the cassettes within the plate handler; b. means for automaticallypositioning the support tables and the cassettes of plates on thesupport tables, and placing a particular table to be loaded with acassette in a cassette loading position; c. means for moving thecassette to be loaded horizontally along a loading platform adjacent tothe cassette loading position and onto the particular table in thecassette loading position; and d. guide means for guiding the cassetteto be loaded of the loading platform and onto the particular table whileloading the cassette into the plate handler.
 13. The apparatus accordingto claim 12, further comprising means for reading information from aninformation source attached to the cassette while moving the cassettefrom the loading platform onto the particular table in the loadingposition.